ASSESSMENT OF ALLELOPATHIC POTENTIAL OF

DIFFERENT WEEDS ON GERMINATION AND

EARLY GROWTH OF AROMATIC RICE

A Thesis

Submitted to

Bangladesh Agricultural University, Mymensingh

In partial Fulfillment of the Requirements

for the Degree of

Master of Science

in

Agricultural Chemistry

By

Monira Yasmin

Roll No.: 10Ag.Chem JD-05M

Registration No.: 32087

Session: 2005-06

Department of Agricultural Chemistry

Bangladesh Agricultural University

Mymensingh

November, 2011

ASSESSMENT OF ALLELOPATHIC POTENTIAL OF

DIFFERENT WEEDS ON GERMINATION AND

EARLY GROWTH OF AROMATIC RICE

A Thesis

Submitted to

Bangladesh Agricultural University, Mymensingh

In partial Fulfillment of the Requirements

for the Degree of

Master of Science

in

Agricultural Chemistry

By

Monira Yasmin

Approved as to style and content by

(Prof. Dr. Md. Mokhlesur Rahman)

Supervisor

(Prof. Dr. Hari Pada Seal)

Co-supervisor

(Dr. Md. Zakir Hossen)

Chairman, BOS and Head

Department of Agricultural Chemistry

November, 2011

ACKNOWLEDGEMENT

All praises are due to the Almighty Allah Whose divine blessing enabled the researcher to complete

her research work and prepare the thesis successfully for the degree of MS in Agricultural

Chemistry.

The author likes to express her gratefulness and indebtedness to her respected supervisor Prof. Dr.

Md. Mokhlesur Rahman, Department of Agricultural Chemistry, Bangladesh Agricultural

University, Mymensingh for his kind advice, valuable guidance and constructive suggestions to

carry out the research work and preparation of this thesis.

The author acknowledges her heartiest gratification and sincere appreciation to her honorable co-

supervisor, Prof. Dr. Hari Pada Seal, Department of Agricultural Chemistry, Bangladesh

Agricultural University, Mymensingh for his sincere advice, planning, upgrading the quality of

the research work and for help in preparing the manuscript of this thesis.

The author humbly desires to acknowledge her sincere gratitude to Prof. Dr. M. Wahid-U-

Zzaman, Prof. Kartik Chandra Saha, Prof. Dr. Md. Akhter Hossain Chowdhury, Dr. Md. Zakir

Hossen, Associate Professor and Head, Dr. Quazi Forhad Kadir, Associate Professor, Dr. Atiqur

Rahman, Assistant Professor, Dr. Razia Sultana, Assistant Professor, Dr. K. M. Mohiuddin,

Assistant Professor, Mrs. Mousumi Akter, Lecturer, Mosammat Hasina Akter, Lecturer and Mr.

Md. Amdad Ali, Lecturer, Department of Agricultural Chemistry for their valuable teaching,

inspiration and encouragement during the whole course of this study.

The author would express her special thanks to the staff members, Department of Agricultural

Chemistry, Bangladesh Agricultural University, Mymensingh for extending all laboratory

facilities for completing research work.

The author is pleased to express her cordial thanks to all of her friends, classmates and well

wishers for their immense inspiration, and kind co-operation during conducting experiment and

writing of the thesis.

The author would like to express heartfelt indebtedness to her respected parents, sisters, friends

and all other relatives for their never ending prayer, encouragement, sacrifice and dedicated efforts

to educate me to this level which can never be forgotten.

The Author

ABSTRACT

A laboratory experiment was carried out at the Department of Agricultural

Chemistry, Bangladesh Agricultural University, Mymensingh to investigate the

allelopathic potential of different weeds on aromatic rice cv. BRRI dhan50. Six

weed species viz., joina (Eimbristylis miliacea), mutha (Cyperus rotundus), khude

shama (Echinochola colonum), sobuj nakful (Cyperus difformis), foskabegun

(Physalis heterophylla) and chapra (Elusine indica) were used in the experiment

to observe their allelopathic effects on seed germination, root length, shoot length

and dry matter production of aromatic rice. Unboiled and boiled weed extracts

reduced the germination and primary growth of aromatic rice. The ranking of

weed species in respect of inhibitory effect on seed germination were Echinochola

colonum > Cyperus difformis > Cyperus rotundus > Elusine indica > Eimbristylis

miliacea > Physalis heterophylla. Khude shama (Echinochola colonum) and sobuj

nakful (Cyperus difformis) had strong detrimental effects on the early growth of

aromatic rice. The relative effect of different weed plant parts (stem, root, leaf and

whole plant) and their concentrations (5, 10 and 25% w/v) were also studied. The

extracts irrespective of plant parts of all weeds inhibited germination and early

growth of aromatic rice. The relative efficiency of reduction of germination and

primary growth by different weed extracts was in the order of stem > root > leaf >

whole plant. The reduction of germination and primary growth of aromatic rice

increased with the increasing extract concentrations. Three unknown compounds

were identified by the TLC technique in extracts of khude shama (Echinochola

colonum) and sobuj nakful (Cyperus difformis). The experimental results proved

that it was important to exclude two allelopathic weeds namely khude shama

(Echinochola colomum) and sobuj nakful (Cyperus difformis) in the aromatic rice

field. It is, therefore, concluded that these two weeds should be avoided from the

aromatic rice field during land preparation.

CONTENTS

Page No.

ACKNOWLEDGEMENT iv

ABSTRACT v

CONTENTS vi

LIST OF TABLES viii

LIST OF FIGURES ix

LIST APPENDICES x

Chapter 1 INTRODUCTION 1

Chapter 2 REVIEW OF LITERATURE 4

2.1 Effect of aqueous extract of different weeds on

germination and primary growth of crops

4

2.2 Effect of different plant parts of weeds on

germination and primary growth of crops

9

2.3 Effect of different concentrations of weed extract on

germination and primary growth of crops

13

Chapter 3 MATERIALS AND METHODS 18

3.1 Test crop 18

3.2 Test weed species 18

3.3 Experimental treatment 18

3.4 Collection of weeds and preparation of weed

extracts

19

3.5 Experimental procedure 19

3.6 Parameters 20

3.7 Experimental data 20

3.7.1 Seed germination 20

3.7.2 Germination time of rice seeds 20

3.7.3 Root and shoot lengths of seedlings 20

3.7.4 Fresh weights of root and shoot of seedlings 20

3.7. 5 Dry weights of root and shoot of seedlings 21

3.8 Identification of chemical compounds 21

3.9 Calculation of Rf values 22

3.10 Data analysis 22

CONTENTS (Contd.)

TITLE Page No.

Chapter 4 RESULTS AND DISCUSSION 23

4.1 Allelopathic effect of different weed species on

aromatic rice

23

4.1.1 Effect of unboiled and boiled weed extracts on

seed germination

23

4.1.2 Effect of unboiled and boiled weed extracts on

primary growth of seedlings

25

4.1.2.1 Root and shoot lengths 25

4.1.2.2 Fresh and dry weights of root 30

4.1.2.3 Fresh and dry weights of shoot 30

4.2 Allelopathic effect of different weed plant parts of on

rice

31

4.2.1 Effect of different weed plant parts on

germination

31

4.2.2 Effect of different weed plant parts on primary

growth

32

4.2.2.1 Root and shoot lengths 32

4.2.2.2 Fresh and dry weights of root 33

4.2.2.3 Fresh and dry weights of shoot 33

4.3 Allelopathic effect of extracts of different weed

plant parts at different concentrations

36

4.3.1 Interaction effect of weed plant parts and

extract concentrations on germination

36

4.3.2 Interaction effect of weed plant parts and

extract concentrations on initial growth

36

4.4 TLC Techniques for extraction of khude shama

(Echinochola colonum) and sobuj nakful (Cyperus

difformis)

40

Chapter 5 SUMMARY AND CONCLUSION 43

REFERENCES 46

APPENDICES 51

LIST OF TABLES

Table TITLE Page No.

4.1 Effect of unboiled weed extracts on germination and

early growth of aromatic rice cv. BRRI dhan50

(Banglamoti)

26

4.2 Effect of boiled weed extracts on germination and early

growth of aromatic rice cv. BRRI dhan50 (Banglamoti)

27

4.3 Allelopathic effect of khude shama extract from

different plant parts on germination and early growth of

aromatic rice cv. BRRI dhan50 (Banglamoti)

34

4.4 Allelopathic effect of sobuj nakful extract from different

plant parts on germination and early growth of aromatic

rice cv. BRRI dhan50 (Banglamoti)

35

4.5 Interaction effect of khude shama extract from different

plant parts on germination and growth of aromatic rice

cv. BRRI dhan50 (Banglamoti)

38

4.6 Interaction effect of sobuj nakful extract from different

plant parts on germination and growth of aromatic rice

cv. BRRI dhan50 (Banglamoti)

39

4.7 TLC of weed extracts and Rf values of the spot 40

LIST OF FIGURES

Figure TITLE Page No.

4.1 Effect of unboiled extract of khude shama (Echinochola

colonum) on aromatic rice seedling

28

4.2 Effect of boiled extract of khude shama (Echinochola

colonum) on aromatic rice seedling

28

4.3 Effect of unboiled extract of sobuj nakful (Cyperus

difformis) on aromatic rice seedling

29

4.4 Effect of boiled extract of sobuj nakful (Cyperus

difformis) on aromatic rice seedling

29

4.5 TLC plates of weed extract of khude shama

(Echinochola colonum) and sobuj nakful (Cyperus

difformis) in ethanol eluted by mixed solvents (A) ethyl

acetate: ethanol (1:1) and (B) benzene : ethyl acetate

(1:1)

41

LIST OF APPENDICES

Figure TITLE Page No.

I Analysis of the variance of the data of unboiled weed

extract on seed germination and early growth of

aromatic rice cv. BRRI dhan50

51

II Analysis of the variance of the data of boiled weed

extract on seed germination and early growth of

aromatic rice cv. BRRI dhan50

51

IIIa Analysis of the variance of khude shama extract

obtained from different plant parts of extract

concentration on seed germination and growth of

aromatic rice cv. BRRI dhan50

52

IIIb Analysis of the variance of sobuj nakful extract obtained

from different plant parts of extract concentration on

seed germination and growth of aromatic rice cv. BRRI

dhan50

52

IVa Analysis of the variance of khude shama extract

obtained from different plant parts and extract

concentration on seed germination and growth of

aromatic rice cv. BRRI dhan50

53

IVb Analysis of the variance of sobuj nakful extract obtained

from different plant parts and extract concentration on

seed germination and growth of aromatic rice cv. BRRI

dhan50

53

CHAPTER 1

INTRODUCTION

Allelopathy refers to the beneficial or harmful effects of one plant on another, both

crop and weed species, by the release of chemicals from plant parts in both natural

and agricultural systems. The term has since appeared commonly in literature to

plant/plant biochemical interactions that causes detrimental effects and it has now

been recognized as an important ecological factor in plant interactions (Chou,

1990). Chemicals with allelopathic potential are present (commonly in conjugated

form) in almost all plant parts and in many tissues like leaves, stems, flowers, fruits,

seeds and roots (Putnam, 1988). Under specific conditions, these chemicals are released

into the environment (atmosphere or rhizosphere) by means of volatilization,

leaching, decomposition of residues, root exudation in ample quantities and long

persistence to affect a neighboring of successional plant (Chou, 1990). These

processes are also affected by environmental complex, and are not easy to single

them out (Einhelling, 1987). The science of allelopathy has progressed its descriptive

and foundations to provide a base to aid crop production.

Weed is an undesirable plant and a serious pest of our crops including

aromatic rice. It competes with crop plants for light, moisture, and other essential

nutrients; as a result it reduces the quality and yield of crops. Its infestation

increases the cost of production, which ultimately reduces the net return, where

there is cultivable land there is weed. Subsistent farmers of the tropics spend more

time, energy and money on weed control than in any other aspects of crop

production (Kasasian, 1971). The harmful effect of weed allelopathy on the

growth and development of field crops are well documented. Plant releasing

chemicals may have deleterious or beneficial effects on other plant growing in

their vicinity. The plant-plant chemical interactions are of vital importance in

agriculture. Phytol, vanillin, 3-methoxy-4hydroxy nitrobenzene and 2, 6-dimethoxy

benzoquinone were isolated from palmer amaranth which inhibited germination

and growth of onion and wheat. These compounds are reported to have inhibitory

influence on germination as well as nutrient assimilation. Commonly cited effects of

allelopathy include the reduced seed germination and seedling growth. Like

synthetic herbicides, there is no common mode of action or physiological target site

for all allelochemicals.

Allelopathic potential may also vary in different parts of an individual weed

species (Bansal and Singh, 1986; Rajangam et al., 1997; Oudhia and Tripathi,

2000). The inhibitory substances present in durba responsible for crop seedling

growth inhibition could retain in every part of the plant and the efficiency in growth

inhibition differs based on the part of the plant (Premasthira and Zungsonthiporn,

1995). Not only that the degree of allelopathic activity of weed species depends on

the concentration of weed material which needs to be investigated (Bhatt et al.,

2001). Allelochemical concentrations in the producer plant may also vary over time

and in the plant tissue produced. Different plant parts including flowers, leaves, stems,

roots, soil and soil leachates and their derived compounds can have allelopathic activity

that varies over a growing season. Allelopathic chemicals can also persist in soil,

affecting both neighboring plants as well as those planted in succession.

Therefore, it is also important to know the effects of different parts of weeds on seed

germination and growth of crop plants.

Therefore, the present study has been undertaken to examine the influence

of some important weeds on germination and primary growth of aromatic rice. A

number of weeds grow in aromatic rice field, which compete with crop and reduce

the crop yield. When the weed shows allelopathic effect, the qualitative and

quantitative damage may be severed on the basis of allelochemicals present in the

species. If the allelopathic effect of specific weed species on particular crop can be

known, weed management becomes economically more effective for the crop

grower. By knowing the potentiality of allelopathy in specific weed, we can remove

those species from the crop field before they contribute allelopathy to crop suppression.

All these information emphasize the study on allelopathy of different weed species

on aromatic rice production. With the above views in mind, the present study was

undertaken to fulfill the following objectives:

i. To observe the allelopathic effects of different weed species on seed

germination and primary growth of aromatic rice cv. BRRI dhan50.

ii. To identify the allelochemicals responsible for the allelopathic effect.

CHAPTER 2

REVIEW OF LITERATURE

The aim of this chapter is to review the results of some previous studies related to

the present research work. In Bangladesh, a few works have been done on allelopathy

but a good number of works have been done in abroad. The research reports

related to the present study are mentioned below:

2.1 Effect of aqueous extract of different weeds on germination and primary growth

of crops

Poly (2009) investigated the allelopathic effect of weeds on wheat cv. BARI

wheat-18 and used five weed species viz., mutha (Cyperus rotundus), foskabegun

(Physalis heterophylla), chapra (Elusine indica), biskataly (Polygonum hydropiper)

and nunia (Portulaca oleracea) to observe their allelopathic effects on

seed germination, root length, shoot length and dry matter production of

wheat. Unboiled and boiled weed extracts reduced the germination and

primary growth of wheat. The ranking of weed species in respect of inhibitory

effect on seed germination was Portulaca oleracea > Polygonum hydropiper >

Elusine indica > Cyperus rotundus > Physalis heterophylla. Biskataly

(Polygonum hydropiper) and nunia (Portulaca oleracea) had strong

detrimental effects on early growth of wheat.

Nasrin (2009) studied the effect of weeds on seed germination and early growth of

jute and soybean. Five weed species viz. durba (Cynodon dactylon), katanotey

(Amaranthus spinosus), baradudia (Euphorbia hirta), haldemutha (Cyperus

esculentus) and shama (Echinochola crusgalli) was used for jute cv. 0-9897 and five

weed species viz., durba (Cynodon dactylon), holdemutha (Cyperus eseulentus),

shama (Echinochola arusgalli), foskabegun (Physalis heterophylla) and chapra

(Elusine indica) was used for soybean cv. Shohag. Boiled and unboiled weed

extracts reduced the germination and primary growth of jute and soybean. Durba

(Cynodon dactylon) and katanotey (Amaranthus spinosus) had strong detrimental

effect on primary growth of jute. Durba (Cynodon dactylon) and foskabegun

(Physalis heterophylla) had also strong detrimental effect on primary growth of

soybean.

An investigation was carried out in typical maize growing sandy loam soil at the

Agronomy Laboratory of Bangladesh Agricultural University, Mymensingh during

March to August, 2000 to determine the allelopathic effect of five weed species viz.,

Polygonum hvdropiper L. (WI), Amaranthus spinosus L. (W2), Chenopodium

album L. (W3), Cyperus rotundus L. (W4) and Imperata cylindrica L. (W5) on

corn (cv. Barnali) seed germination, growth and development (Samad et al.,

2008). The trial included dried plant parts of five selected weeds (the whole plant,

stem, leaf, root and five weed mixture) and weeds aqueous extract (whole plant,

stem. leaf; root and five weed mixture) in petridishes at laboratory condition.

These five weed species exhibited inhibition of seedling height and radicle

length. Imperata cylindrica affected the seedling height and seedling dry matter

production severely than others. Radicle length was affected by Amaranthus

spinosus. On the other hand, germination, seedling growth and dry matter

production affected maximum by dried mass of stems of five weed species.

The results demonstrated the allelopathic potential of five weed species and

suggested that those weed species might affect corn seedling growth and

development due to the inhibitory effect of allelochemicals, which were present in

the dried parts and aqueous extracts of weed.

Zoheir et al. (2008) stated that the experiment barley (Hordeum vulgare) contained

water soluble allelochemicals that inhibited the germination and growth of other

species. Greenhouse and laboratory experiments were conducted to determine the

effects of barley leaf, stem, flower and root water extract concentrations on green

loxtail (Setaria viridis) germination and seedling growth. In bioassays, barley

extracts reduced green foxtail hypocotyl length, hypocotyl weight, radicle weight,

seed germination and radicle length when compared with water control.

Khatun (2008) studied the effect of weeds on seed germination and primary growth

of rice and mungbean. Four weed seed species viz., durba (Cynodon dactylon),

shama (Echinochloa crusgalli), biskatali (Polygonum hydropiper), and foskabegun

(Physalis heterophylla) were selected. Boiled and unboiled weed extracts reduced the

germination and primary growth of rice and mungbean. The ranking of weed species

in respect of inhibitory effect on seed germination of BARI Mung-5 and BINA

moog5 was Physalis heterophylla > Cynodon dactvlon > Echinochloa crusgalli >

Polygonum hydropiper. Durba (Cynodon dactylon) and foskabegun (Physalis

heterophylla) had strong detrimental effect on primary growth of these varieties. The

extracts of all parts (e.g. stem, root, leaf; and whole plant) of weeds inhibited

germination and primary growth of this variety.

Hua et al. (2007) investigated a series of experiments to evaluate the phytotoxicity

and to identify the allelochemicals of Ambrosia trifida against wheat (Triticum

aestivum). The results showed that wheat growth could be significantly inhibited

in Ambrosia trifida infested, or residue amended soils in North-East China. Two

carotane-type sesquiterpcnes, l alpha (angeloyloxy) -carotol and l alpha-(2-methyl

butyrovloxy)-carotol were subsequently isolated and identified from the toxic

soils. Both compounds had high inhibitory activity on wheat growth.

A study was carried out by Batiste et al. (2007) to determine the potential and

nature of root-mediated allelopathic interference of Chenopodium murale on

wheat. Early growth of wheat reduced significantly in agar medium where

C. murale seedlings were previously growing as well as in rhizosphere soil of

C. murale. The reduction in wheat growth was due to the presence of inhibitory

metabolites released by roots of C. murale in the growth media. Even the soil

incorporation of root residues also reduced the wheat growth in terms of seedling

length and seedling dry weight. Root residues did not reduce the available

nutrients in the soil, which was rather nutrient rich. These results indicated the

definite role of allelopathy of C. murale roots in retarding wheat growth.

A laboratory experiment was conducted by Roy et al. (2006) to determine the

influence of naturally occurring growth substances in aqueous extracts of some

common weeds of naturally occurring growth substances in aqueous extracts of

some common weeds, i.e. bathua (Chenopodium album), bhijli ghash (Striga

deniflora), shetdrone (Leucus aspera), mutha (Cyperus rotundus), chapra (Elcusine

indicu) and khude anguli (Digitaria ischaemum) on delayed germination and

growth of wheat and jute seeds. Boiled and unboiled extracts of all weed

species significantly reduced and delayed the germination of wheat and jute

seeds. The effect of boiled and unboiled bathua extracts showed the lowest

germination in wheat seeds. Root and shoot lengths of wheat and jute were also

decreased due to the presence of weed extracts.

Laboratory based studies were undertaken by Shahid et al. (2006) to assess

the allelopathic effect of different aqueous extracts of plants viz., sorghum

(Sorghum bicolor), sunflower (Helianthus annuus), johnson grass (Sorghum

halepense), eucalyptus (Eucahptus camaldulensis) and acacia (Acacia nilotica)

on wheat and its weeds. Analysis of data (taken twenty days after seedling) revealed

that germination percentage, shoot length, root lengths and biomass plant were

significantly (P < 0.001) inhibited by plant extracts. Sunflower extract was the

most inhibiting to germination, shoot and root length of wheat and to all species

of weeds, while application of johnson grass extract resulted in significantly

minimum biomass plant.

Kayode (2004) investigated to evaluate the effects of 24 and 48 h C.

procera leaf extracts on the radicle and plumule growth of maize cultivars Oba

Super I, II, III and IV. Both extracts showed considerable inhibitory effects on

radicle and plumule growth of the cultivars. The severity of inhibition increased

with an increase in the duration of the extraction. The growth of Oba Super I

was the least inhibited while the growth of Oba Super III was the most inhibited

by the extracts when the growth and development of the plumule were compared

to those of the control.

Agarwal et al. (2002) found that weed extracts of Avena futua, Cyperus rotundus,

Polygonum hydropiper and Solanum nigram inhibited the length of plumule in all

the varieties of wheat.

Ameena and George (2002) assessed the allelopathic effect of aqueous extracts of

purple nutsedge (Cyperus rotundus) on the germination and seedling growth of

okra (Abelmoschus esculentus). Result showed that aqueous extracts of nutsedge

dry plant parts inhibited the germination and seedling growth of okra. Inhibition

was dependent on concentration.

Bhatt et al. (2001) reported the allelopathic influences in bioassays on Glycine

max cv. JS-80-21, Vigna mungo cv. DPU-80-31, Oryza sativa cv. RCPL-129

and Zea mays cv. Vijay. The aqueous extracts of dried and fresh leaves of weeds

significantly suppressed the germination. Toxicity increased with the increased

concentration of extracts. The effect of extracts was greater on germination of Vigna

mungo and Oryza stliva compared to Glycine max and Zea mays.

Binita et al. (2001) performed a study on allelopathic effect of eight important

weeds commonly grown in North East India, namely Amaranthus sp, Argemone

mexicana, Cynodon dactylon, Cyperus rotundus, Imperata cylindrica, Luntunu

curnuru, Parthenium hysterophorus and Chenopodium sp. on different vegetable

production. Of them Cynodon dactylon and Parthenium hysterophorus showed

both stimulatory effect on germination and seedling of growth of vegetables.

Olofsdotter (1999) conducted a research in soybean allelopathy and utilization in

weed management program in Egypt. Korea, India and Sri Lanka and observed that

the allelopathy effect of Glycine max on different concentrations. The leaf extracts

have significant stimulatory or inhibitory effects on germination or seedling vigor

of soybean and shoot elongation of rice.

Oudhia et al. (1999) conducted an experiment and found that the effect of the

aqueous extracts of different plant parts of Blumea lacera produced significant

effects on the germination and seedling vigour of rice. At 3 days after sowing

(DAS), root extracts obtained after 11 days of decay enhanced seed germination.

At 5, 7, 9 and 11 DAS, leaf extracts obtained after 9 days of decay produced

the highest percentage of seed germination. Different parts of I3. lacera failed

to produce any detrimental effect on any weed species.

Oudhia and Tripathi (1998) stated the allelopathic effects of Sesamum inclicum,

Helianthus annus, Catharanthus rosea, Bombax ceiba and Acacia auriculaeformis

on germination and seedling vigour of rice cv. Mahamaya. The fresh samples of

leaves of these plants were cut into line pieces, immersed in water and decayed for

24 h in the ratio of 1:10 (w/v). The extracts were applied to rice seeds. Different

extracts produced significant effect on germination and seedling vigour. C. roseus

extracts gave very low germination after 3 days, although by 5 days after sowing

there were no significant differences between treatments.

Rahman et al. (1996) performed an investigation with aqueous extracts of some

common weeds viz., katanotey (Amaranthus spinosus L.), shama (Echinochloa crusgalli),

durba (Cvnodon dactylon L.), lazzabati (Mimosa pudica L.), mutha (Cyperus rotundus

L.), baradhudhia (Euphorbia hirta L.) and haldemutha (Ctiperus esculentus L.). Boiled

and unboiled extracts of katanotey, durba and lazzabati reduced the germination and

early growth of rice while all the 7 weed species inhibited germination and growth of

jute. The extracts of all weeds delayed the germination of rice and jute seeds.

2.2 Effect of different plant parts of weeds on germination and primary

growth of crops

Sharma (2005) evaluated the allelopathic effects of some newly developed strains

of harar (Terminalia chebula) and reetha (Sapindus mukorossi) on wheat (Triticum

aestivum), maize (Zea mays), gram (Vigna sp.), lentil (Lens culinaris), pea (Pisum

sativum) and brinjal (Solanum melongena). Leaves of 6 strains of Terminalia

chebula and two strains of Sapindus mukorossi were collected and allowed to

shade dry. The treated crops responded differently to aqueous leaf extracts

of Harar and Reetha indicating the presence of different phytoactive compounds

and growth promoters. Some strains had synergistic or no adverse effect on germination

and growth of tested field crops, whereas other had antagonistic effects.

An aqueous leaf and root/tuber extracts of three important medicinal plant

species (e.g. Bergenia ciliates, Hedychium spicatum and Potentilla fulgens) were

tested by Basotra et al. (2005) for their allelopathic effects on germination,

radicle and plumule elongation of Amaranthus caudatus, Eleusine coracana,

Fagopyrum esculenttum, Vigna mungo, Phaseolus vulgaris and Triticum aestivum.

The results revealed that the allelopathic effects increased with increasing

concentration of leachats from 2, 5 to 10%. The susceptible crops were Amaranthrrs

caudatus and Phaseolus mungo whose germination, radicle and plumule growth

were reduced significantly under aqueous extracts of all three medicinal

species.

A greenhouse experiment was conducted by Narwal et al. (2003) to evaluate the

allelopathic effects of different parts of sunflower biomass (stem, leaf infloresence

and root) on winter wheat. Among the different parts of sunflower, stems showed

the highest inhibitory effect on the growth and yield of wheat, followed by the

roots, leaves and infloresences. Increasing doses of sunflower biomass resulted in

significant reductions in the seedling growth and yield of wheat.

Zoheir et al. (2008) stated that increasing the extract concentrations from 4 to 20 g per

100 mL of water of all barley parts significantly increased the inhibition of green

foxtall germination, seedling length and weight. Based on 7-day old green foxtail

redicle length, averaged across all extract concentrations and the degree of toxicity

of different barley plant parts were ranked in the following order of inhibition:

leaves > flowers > mixture of all plant parts > stems > roots.

Khatun (2008) conducted an experiment to observe the allelopathic effect of weeds

on seed germination and primary growth of rice and mungbean. Four weed seed

species viz., durba (Cynodon dactylon), shama (Echinochola crusgali), biskatali

(Polygonum hydropiper) and foskabegun (Physalis heterophylla) are selected. She

also stated that the relative efficiency of inhibition of germination and primary growth

by different weed plant parts was in the order of stem>whole plant> leaf > root.

An attempt was made to evaluate the effect of durba (Cynodon dactylon L.)

extracts on seed germination and early seedling growth of jute and mungbean.

The experiment was conducted by Rahman et al. (2006) during the period between

August and October 2005. Durba plants were collected from the Agronomy Field

Laboratory of Bangladesh Agricultural University on 14 August and extracts of 1,

5, 10 and 25% concentration (w/v) were prepared from leaves, stems, roots

and whole plants. The extracts of different parts of durba plant reduced

germination and early growth of both crops. The relative efficiency of

inhibition of germination and growth by different extracts were in the order of

stem>whole plant>leaf>root. Between the crops, jute was more sensitive to

allelochemical action. The reduction of germination and growth for both crops

increased with increasing extract concentration.

Mulatu et al. (2005) found that aqueous extracts of Parthenium hysterophorus leaf

and flower seriously inhibited seed germination and seedling growth (root and

shoot lengths) of lettuce. Extracts of the root and stem had much less effect.

Lettuce roots were more sensitive to the allelopathic effect than shoots. It

appears that early removal of Parthenium weed from lettuce fields is essential

to avoid poor germination and seedling growth.

Gamez et al. (2002) conducted an experiment on the allelopathic effect of

extracts from the stem and leaves of Cynodon dactylon and Sorghum halepense

on seeds of oat cv. L138, wheat, sorghum and bean. The stem extract decreased the

respiration rate in wheat and oat. Weed extracts inhibited germination and dry

matter accumulation in the crops.

Meena (2001) investigated the allelopathic effect of the aqueous extracts of shoots

and tubers of purple nutsedge (C. rotundus) at 2.5, 5.0, 7.5 and 10% concentration on

germination and seedling growth of pigeon pea and mungbean. An increase

in aqueous extract concentration of shoot and tuber of nutsedge reduced seed

germination and seedling growth of pigeon pea and bean. The negative allelopathic

effect was more pronounced with tuber extract than shoot extract on all growth

attributes of both the pulses i.e. germination, fresh weight, dry weight of radicle

and plumule, redicle length, plumule length, leaves plant-1

and secondary roots

plant-1

.

Allelopathic effects of Parthenium hysterophorus on seed germination of rice

were investigated by Oudhia et al. (1999). Root, stem, leaf and stem + leaf

sections of P. hysterophorus were cut into fine pieces, immersed in water and

left for 120, 168, 216 or 264 h at room temperature (22 ± 1°C) at a ratio of

1:10 (w/v). The extracts were than applied to rice seeds. The extracts had

significant allelopathic effects on rice germination and seedling vigour. At 11

days after sowing (DAS), the 216-h stem + leaf extract and the 120-h stem+

leaf extract resulted in the greatest and lowest levels of germination,

respectively.

Beres and Kazinczi (2000) assessed the effect of aqueous extracts of shoots and

plant residues of Abutilon theophrasti, Amaranthus retroflexus, Asclepias syrica,

Chelidonium majus, Chysvnthemum vulgare, Datura stramonium, Rumex

obtusifolius and Solidago gigruttea on the germination and growth of barley,

maize, soybeans, sunflower and wheat in petridishes and pot experiments.

Shoot extracts of S. gigantea and A. theophrasti reduced germination of wheat

by 7.6 and 18.3%, respectively, and germination of barley by 9.8 and 2.7%.

Extracts of A. svriaca, C. vulgare and D. stramonium reduced germination of

maize by 34, 30 and 44%, respectively. The extracts of all weeds studied, except

A. retrofexus, reduced germination of sunflower and soybean. In bioassays, extracts

of A. syriaca, A. theophrasti and S. gigantea increased the fresh weight of wheat

plants. The weight of barley was increased by extracts of 5 weeds. In pot experiments

with weed residues, germination of test crops was inhibited, but fresh weight of

crop seedlings was stimulated.

Kalita et al. (1999b) reported that the aqueous extracts of Cynodon dactylon

and Cyperus rotundus at concentrations of 1:5 and 1:10 w/v had significant

allelopathic effects on seed germination of rice. Aqueous shoot extracts were

inhibitorier than root extracts at the same concentration.

Bora et al. (1999) studied the allelopathic effect of fresh extracts of Acacia

aurculiformis on seed germination and radicle and plumule elongation of rice (Oryza

sativa), mustard (Brassica campestris) and gram (Cicer arietinum). The inhibitory

effect of leaf extract on germination was proportional to the concentration of the

extracts. The elongation of radicle and plumule was reduced in all treatments, with

effects much more pronounced on plumule than radicle elongation.

Oudhia and Tripathi (2000) conducted an experiment on allelopathic effect of

Lantuna camara on rice and reported that the extracts of root, stem, leaf and

stem + leaf tissue of L. camara had significant effects, increasing rice germination

rates and seedling vigour.

2.3 Effect of different concentrations of weed extract on germination and

primary growth of crops

Channappagoudar et al. (2005) studied the allelopathic effects of extracts of

Cyperus rotundus, Commelina benghalensis, Parthenium hysterophorus and

Prosopis julilora leaves collected from karnataka, India at two concentrations (5 and

10% w/v) on sorghum, wheat, green gram, soybean, sunflower and groundnut in

the laboratory. The results revealed that Commelina and Cyperus extracts had

greater inhibitory effect on germination, seedling length and seedling vigour

index than the leaf extracts of the other crops.

Laboratory experiments were conducted by Yao et al. (2006) to study the potential

role of allelopathy in plant interference and in the successful invasion of

alien species Salidago canadensis. Aqueous and ethanolic extracts were used

as treatment solutions to assess their effects on seed germination and

seedling growth in four target species, mulberry (Morns alba), morning glory

(Pharbitis nil), wheat (Triticum aestivum) and rape (Brassica campestris).

Reduction and/or growth in germination and growth of the target plant

species in the presence of both aqueous and ethanolic extracts at different

concentrations indicated that the responses were species-specific and concentration

dependent. Generally, ethanolic extracts (especially from leaves) imposed stronger

effects on both seed germination and seedling growth. Extracts with lower concentration

at 0.001 g mL-1

dry weight could stimulate seedling growth of rape and morning

glory, where as extracts at the higher concentrations have inhibitory effects on

mulberry.

Khatun (2008) studied the effect of weeds on seed germination and primary

growth of rice and mungbean. Four weed seed species viz., durba (Cynodon

dactylon), shama (Echinochloa crusgalli), biskatali (Polygonum hydropiper) and

foskabegun (Physalis heterophylla) were selected. Boiled and unboiled weed

extracts reduced the germination and primary growth of rice and mungbean.

The ranking of weed species in respect of inhibitory effect on seed germination

of BARI Mung-5 and BINA moog5 was Physalis heterphylla> Cynodon dactylon >

Echinochloa crusgalli > Polygonzun hydropiper. Durba (Cynodon dactylon) and

foskabegun (Physalis heterophylla) had strong detrimental effect on the primary

growth of these varieties. The extracts of all parts (e.g. stem, root, leaf, and whole

plant) of weeds and their concentrations (5, 10 and 25% w/v) inhibited germination

and primary growth of this variety. She also conducted that the reduction of

germination and primary growth for both crops increased with increasing extract

concentration.

Hassan and Samy (2007) conducted the experiment to study the effect of dry

leaf water extraction (5, 10, 20, 40 and 60%) of Calotropis procera plants on

the germination of barley (Hordeum vulgare L.), wheat (Triticum aestivum L.),

cucumber (Cucumis satirus) L., fenugreek (Trigonella foenum graecum L.) and

alssana (Senna occidentalis L. Link). The results showed that the germination

delayed at the higher concentrations and the final germination percentage was

decreased by increasing leaf extract concentration. Generally, the radicle and

plumule growth was sensitive to different levels of leaf extraction whereas,

the radicle length was decreased by increasing the extract concentration.

Dongre and Yadav (2005) performed an experiment to observe the inhibitory

effect of leaf leachates on seed germination of pea (Pisum sativum). Seeds of

pea (Pisum sativum) cultivars, Arpan and Malviya 2 sapana were treated with

different concentrations of aqueous leaf leachates of 8 dominant weeds (Ageratum

conzoides, Anagallis arvensis, Eclipta alba, Lippia nodiflora, Parthenium hyterophorus,

Phyllanthus niruri, Pluchea lanceolata and Polygonum plebejum) to assess their

allelopathic effects on seed germination. Fifty seeds of each cultivar were

placed equidistantly in 10 cm diameter petridish plates with 2 layers of filter paper.

Approximately 15 mL of 10, 20, 30 and 40% leachates from each weed species

were poured into the specified petri plate. Leachates of all weed species inhihited

both percent seed germination and seedling growth of both test cultivars at 10%

concentration was invariably associated with further decrease in germination performance

of each test cultivar irrespective of weed species.

Deka et al. (2004) conducted an experiment to study the effect of leaf

extracts and leachates of the weeds namely Dryinaria cordata and Oplismenus sp. on

the germination and growth of seeds of Raphanus sativus. The extract and leachate

were diluted with distilled water and applied at 1:2, 1:4, 1:8 and 1:16, and

1:10, 1:20, 1:40 and 1:80 v/v, respectively. Higher inhibition of seed germination by

D. cordata extracts showed that the allelochemicals from D. cordata were more

toxic on radish seed than Oplismenus sp.

Veenapani et al. (2004) performed an experiment to study the effect of

Paspalum scrobiculatum and Echinochloa colonum on rice seed germination. Rice

seeds were placed in petridish lined with three layers of filter paper

moistened with aqueous leachates (1:0, 1:5, 1:10, 1:25, 1:50, 1:100, 1:250 and

1:500 dilutions) from leaves, stem, roots and seeds of both weeds. The

percentage of reduction in germination was 39.6, 36.0, 10.0 and 5.0% with

leaf, steam, root and seed extracts of P. scrobiculatum and 60.0, 3.0, 7.0 and

20.0% with leaf, stem, and root and seed extracts of E. colonum. These results

indicated the allelopathic effects of both weeds on rice seed germination.

Meena (2001) conducted an experiment to assess the allelopathic effect of the

aqueous extracts of shoots and tubers of purple nutsedge (C. rotundus) at 2.5, 5.0,

7.5 and 10% concentration on germination and seedling growth of pigeon pea

and mungbean. An increase in aqueous extract concentration of shoot and tuber of

nutsedge reduced seed germination and seedling growth of pigeon pea and mungbean.

Kalita et al. (1999a) performed an experiment to assess the allelopathic effect of four

common upland rice weed species (Ageratum conzoides, Borreria hispida, Cynodon

dactylon and Cyperus rotundus) on leaf area per plant, total leaf chlorophyll content

and leaf nitrate reductase activity of potted rice plants at 25 to 50 days after sowing

(DAS). The weeds were sundried, ground and mixed with rice potting soil at rates of

1:5, 1:10, and 1:20 w/w. The greater the concentration of weed residue, the greater

was the reduction of all tested parameters in rice plants at both 25 and 50 DAS.

Casini et al. (1998) performed an experiment to study the effects of four aqueous

extracts (0, 1.0, 2.0, and 3.0% w/v) of itch grass (Rottboellia cochinchinensis) and

cogon grass (Imperata brasiliensis) on rice germination and the effects of residues

(0, 1.0, 2.0, and 3.0% w/w) incorporated in the growth medium on early rice plant

development were tested. Allelochemicals present in weed extracts reduced germination

of rice by 11-15% at the highest concentration. A different effect of residues on total

dry matter of seedlings was observed. The lowest concentration of water extracts of

weeds increased epicotyl length and reduced the germination index.

Rajangam (1997) evaluated that the allelopathic effects of the weed Heliotropiwn

indicum on germination, growth and biochemical composition of paddy. The experiment

was conducted in petridishes and pots in the laboratory. An aqueous extract

of fresh leaves, shoots and roots of H. indicum inhibited germination of the rice

varieties IR-20 and Ponmani.

This review suggested that the potentiality of allelopathy may vary in different plant

parts of an individual weed species. Allelopathic substances are most commonly found

in plant extracts. A number of weed species possess allelopathic potential which suppress

the growth of field crops including rice, wheat, jute, soybean, mungbean, lentil and so

on. The per cent reduction also depends on the concentration of the aqueous extracts

of weed species. Therefore, the allelopathic effects of six weed species on aromatic rice

seed germination were studied and at the same time, the effects of different plant

parts were also taken into consideration with different concentrations.

CHAPTER 3

MATERIALS AND METHODS

An experiment was conducted at the Departmental Laboratory of Agricultural Chemistry,

Bangladesh Agricultural University, Mymensingh during the period from September

to November 2011 to evaluate the allelopathic effect of weed extracts on germination

and primary growth of aromatic rice.

3.1 Test crop

Aromatic rice cv. BRRI dhan50 (Banglamoti) was used as test crop in this

experiment.

3.2 Test weed species

The following common weed species were selected for this study:

Sl.

No.

Bengali name English name Scientific name

1 Joina Cogon grass Eimbristylis miliacea

2 Mutha Purple nutsedge Cyperus rotundus

3 Khude shama Small burnyardgrass Echinochola colonum

4 Sobuj nakful Smallflowered umbrellagrass Cyperus difformis

5 Foskabegun Clammy groundcherry Physalis heterophylla

6 Chapra Indian goosegrass Elusine indica

3.3 Experimental treatment

The boiled and unboiled extracts of the selected weeds were used for test crop. Stem,

leaf, root and whole plant extracts of different weed species were considered in this

experiment. For each weed 5, 10 and 25% of plant part extracts including control

(only water) were applied.

3.4 Collection of weeds and preparation of weed extracts

Weed species collected from the Agronomy Field Laboratory, Bangladesh Agricultural

University, Mymensingh were joina (Fimbristylis miliacea), mutha (Cyperus

rotundus), khude shama (Echinochola colonum), sabuj nakful (Cyperas

difformis), foskabegun (Physalis heterophylla) and chapra (Elusine indica).

After collection, they were washed, chopped and macerated. In a set, fresh weed

mass (250 g) of each weed species was boiled in 1 L water and kept for 3

days with intermittent stirring. The extracts were filtered through filter paper

(Whatman No. 1). The filtrates were used as boiled extracts of weeds. In another set,

250 g fresh weed mass were decomposed in 1 L water for 7 days at normal room

temperature. The extracts were filtered and used as unboiled extract. Thus boiled and

unboiled extracts of each weed species were prepared and used in this experiment

following the technique as stated by Prasad and Srivastava (1991).

In another trial, the collected weed plants were separated into four portions viz.,

leaves, stems, roots and whole plants. Fresh weed portions were chopped and

macerated and 125 g of each portion were decomposed in 500 mL, distilled water

for 7 days at room temperature (28 ± 1°C) with intermittent stirring. The extracts

were filtered through filter paper (Whatman No. 1). From the filtrate 5, 10 and

25% (w/v) extract solutions were prepared from each portion of selected weeds.

3.5 Experimental procedure

The effect of weed extracts on the germination of aromatic rice cv. BRRI dhan 50

seeds were tested in petridishes in the laboratory. Two sets of trial, with

boiled and unboiled extracts were performed. Twenty five seeds of aromatic

rice were placed in each petridish lined with double layer of filter paper and

treated with weed extracts. Fifteen milliliter aqeous extracts of different weeds

were put in each petridish and a control set with distilled water was run

simultaneously every time. The filter papers were kept constantly moist with

distilled water. The experiment was arranged in a completely randomized design

with 3 replications at room temperature (28 1°C).

3.6 Parameters

The following parameters were considered in this study:

a) Germination (%)

b) Days to complete germination

c) Seedling growth and weight

i) Root and shoot lengths

ii) Root and shoot weights

In this experiment, 10 plants were selected to each parameter and the average

results were calculated from these collected plants.

3.7 Experimental data

Experimental data were collected on the following parameters.

3.7.1 Seed germination

The number of germinated seeds was counted from the beginning of seed

germination up to completion of the seed germination.

3.7.2 Germination time of rice seeds

Mean germination time was calculated after counting germination.

3.7.3 Root and shoot lengths of seedlings

The root and shoot lengths of aromatic rice seedling were measured after

7 and 14 days, respectively.

3.7.4 Fresh weights of root and shoot of seedlings

The fresh weights of respective root and shoot of aromatic rice seedling were

measured after 7 and 14 days of the germination setting.

3.7. 5 Dry weights of root and shoot of seedlings

The dry weights of respective root and shoot of aromatic rice seedling were

measured after 7 and 14 days of the germination setting.

3.8 Identification of chemical compounds

Thin layer chromatography (TLC) was developed to identify the compound using

different polar and nonpolar solvent systems such as chloroform, petroleum ether,

ethyl acetate and methanol following the technique as stated by Chopra and Kanwar

(1980) and Ahuja (2003). Thin layer chromatographic (TLC) technique was employed

for the identification of the number of compounds present in extracts of khude shama

(Echinochola colonum) and sabuj nakful (Cyperus difformis). The chromatographic

plates were prepared by spreading a suspension of finely powdered silica gel for TLC

on glass plates of suitable sizes (5 1 0.3 cm3). About 50 g silica gel was mixed

thoroughly with 125 mL of water in a beaker. This was then spread unifomly on clear

glass plates with the help of a spreader. The silica coated plates were then dried in an

oven at 105 ± 5°C for about 12 hours before use. Freshly prepared plates were always

used for TLC.

A number of solvent chambers were prepared by solvents of low to high polarity

and by some mixed solvents of expected polarities. For obtaining a chromatogram, a

minute drop of khude shama (Echinochola colonum) and sabuj nakful (Cyperus

difformis) extract in a suitable solvent (ethanol, boiling and normal distilled

water) was applied with a capillary tube along a bare line along at the bottom of

the plate. This was then developed in a TLC tank containing selected solvent or

mixed solvents. The sample gave both coloured and colourless spots on the TLC

plate in ordinary conditions. To locate colourless spots, the developed plates were

further treated in various ways and kept for some time in gaseous iodine chamber.

TLC of extracts using different solvents as eluent gave spots for different compounds

present in the extracts. Considering the Rf values and the respective polarities of

the eluent, the polar nature of the compound and its extent was ascertained. TLC

of the extracts was made using different solvents and mixed solvents. A number

of spots were observed for different compounds and their Rf values were determined.

3.9 Calculation of Rf values

When solvent passed more than half of the TLC plate, it was marked and the

plates were taken out and allowed to dry. The plants were then placed in iodine

chamber and Rf (Ratio of flow) values were calculated as follows:

pointstartingthefromfrontsolventthebytraveledDistance

pointstartingthefrommoleculescomponentthebytraveledDistancef

R

3.10 Data analysis

The collected data on various parameters were statistically analyzed. The means

for all treatments were calculated and analysis of variance for all characters was

performed by F-test. The significance of difference between the pairs of means

was calculated by LSD as reported by Gomez and Gomez (1984).

CHAPTER 4

RESULTS AND DISCUSSION

This chapter depicts the presentation of the experimental data through different

forms of illustrations. The possible interpretation of major findings has also been

made. The experimental results have been presented and discussed in this chapter.

The whole discussion has been categorized as the effect of weed extracts on seed

germination, shoot and root lengths, fresh and dry weights of root and shoot of

aromatic rice cv. BRRI dhan50 (Banglamoti) as follows:

4.1 Allelopathic effect of different weed species on aromatic rice

4.1.1 Effect of unboiled and boiled weed extracts on seed germination

The experimental data on the effect of unboiled and boiled weed extracts on seed

germination have been shown in Tables 4.1- 4.2, Figs. 4.1-4.2 and Appendix is I-

II. It was found that seed germination varied significantly due to the effect of

unboiled and boiled weed extracts on seed germination of aromatic rice cv. BRRI

dhan50.

Aromatic rice germination was reduced significantly by the allelopathic effect of

different weed species (Table 4.1). In case of unboiled extract, maximum germination

rate (96.2%) was observed in control and minimum rate (80.8 %) was found in khude

shama (Echinoahla colonum) extract treated seeds (Table 4.1). It was observed that

germination rate was comparatively higher due to less allelopathic effect of

Physalis heterophylla (93.0%), Eimbristylis miliacea (91.6%), Elusine indica

(91.0%), Cyperus rotundus (89.3%) and Cyperus difformis (82.5%) extract treated

seeds. The ranking of weed species in respect of inhibitory effect on seed

germination of aromatic rice seed was Echinochola colonum > Cyperus difformis

> Cyperus rotundus > Elusine indica > Eimbristylis miliacea > Physalis heterophylla.

Again, days required to complete the germination of seeds was also affected significantly

by weed extracts. Minimum days (3.00 days) required to complete the germination

was recorded in control treatment where as maximum days (7.00 days) was due to the

effect of Echinochola colonum extract treated seeds. Therefore, the effect of unboiled

extracts of different weed species induced statistically significant variation in germination

rate and number of days required to complete the germination of aromatic rice seeds.

In case of boiled extract, maximum germination rate (95.5%) was observed in

control and minimum rate (75.5%) was found in khude shama (Echinochola

colonum) extract treated seeds (Table 4.2). It was observed that germination rate

was comparatively higher due to less allelopathic effect of Physalis heterophylla

(92.8%), Embristyis miliacea (91.2%), Elusine indica (90.3%), Cyperus rotundus

(90.3%) and Cyperus difformis (83.3%) weeds had strong inhibitory effect on

seed germination of aromatic rice. The ranking of selected weed species in respect

of inhibitory effect on seed germination of aromatic rice was Echinochola colonum

> Cyperus difformis > Cyperus rotandus > Elusine indica > Eimbristyis miliacea

> Physalis heterophylla. Similar inhibitory effect was noted by Roy (1995). Agarwal

et al. (2002) found the inhibitory effect on germination and seedling growth of all

varieties of mustard. Results of this study suggested that the germination of

aromatic rice seed in the field might be reduced by the presence of weed species,

especially Echinochola colonum and Cyperus difformis due to their allelopathic

influence.

Again, days required to complete the germination of seeds was also affected

significantly by weed extracts. The lowest number of days (3.00 days) required to

complete the germination was recorded from control treatment and extract treated

seeds whereas maximum days (7.00 days) was due to the effect of Echinochola

colonum extract treated seeds (Table 4.2).

In case of boiled extract, days required to complete the germination of seeds was

also affected significantly by weed extracts. The lowest number of days (4.10 days)

required to complete the germination was recorded from control treatment and

weed extract treated seeds whereas maximum days (6.23 days) was due to the

effect of khude shama (Echinochola colonum) extract treated seeds (Table 4.2).

4.1.2 Effect of unboiled and boiled weed extracts on primary growth of

seedlings

4.1.2.1 Root and shoot lengths

The result revealed that unboiled and boiled weed extracts reduced root and shoot

lengths of aromatic rice cv. BRRI dhan50 significantly (Tables 4.1-4.2 and Appendix

is I-II). Root and shoot lengths of aromatic rice were affected significantly by the

allelopathic effect of different weed species. Root and shoot lengths of aromatic rice

showed significant reduction due to the treatment of seeds with unboiled and

boiled weed extracts. In case of unboiled extract, the highest root length (8.25 cm) of

aromatic rice seeding was observed in control treatment and the lowest root length (3.50

cm) was obtained in khude shama (Echinochola colonum) extract treated aromatic rice

seedling (Table 4.1). In case of boiled extract, the highest root length (8.00 cm) of

aromatic rice was observed in control treatment and the lowest root length (3.25 cm)

was found in khude shama (Echinochola colonum) extract treated aromatic rice

seedlings (Table 4.1).

Fig. 4.1 Effect of unboiled extract of khude shama (Echinochola

colonum) on aromatic rice seedling.

Control Khude shama (UBE)

Control Khude shama (BE)

Fig. 4.2 Effect of boiled extract of khude shama (Echinochola

colonum) on aromatic rice seedling.

Fig. 4.3 Effect of unboiled extract of sobuj nakful (Cyperus

difformis) on aromatic rice seedling.

Control Sobuj nakful (BE)

Control Sobuj nakful (UBE)

Fig. 4.4 Effect of boiled extract of sobuj nakful (Cyperus difformis)

on aromatic rice seedling.

Again, maximum shoot length (9.87 cm) of aromatic rice seedling was noted in

control treatment and minimum shoot length (4.00 cm) was recorded in unboiled

extract of khude shama (Echinochola colonum) and joina (Eimbristylis miliacea)

. Again, maximum shoot length (9.50 cm) of aromatic rice seedling was noted in

control and minimum shoot length (3.80 cm) was recorded in boiled extract of

khude shama (Echinochola colonum) as presented in Tables 4.1-4.2. Similar results

were reported by Prasad and Srivastava (1991) and Qasem (1993). Reduced shoot

and root lengths were observed in this experiment was possibly due to the effect

of allelochemicals of weed species under investigation.

4.1.2.2 Fresh and dry weights of root

The effect of unboiled and boiled extracts of weeds on aromatic rice seedling

reported in Tables 4.1-4.2 indicating significant reduction on fresh and dry

weights of root of seedlings. In case of unboiled weed extract, maximum fresh

(5.81 mg) and dry (4.25 mg) weights of root were recorded in control treatment.

On the other hand, minimum fresh (2.17 mg) and dry (1.53 mg) weights were

recorded in unboiled extract of khude shama (Echinochola colonum).

In case of boiled weed extract, maximum fresh (6.25 mg) and dry weights (4.15

mg) were observed in control treatment. Minimum fresh (2.16 mg) and dry (1.20

mg) weights of root were found in boiled extract of Echinochola colonum (Table

4.2). Fresh and dry weights of root of aromatic rice seedling were inhibited significantly

by allelopathic effect of different weed species.

4.1.2.3 Fresh and dry weights of shoot

Fresh and dry weights of shoot of aromatic rice seedlings were affected significantly

by the allelopathic effect of different weed species. Maximum reduction of shoot

weight was found due to the treatment of seeds within Echinochola colonum

extract. Maximum fresh (8.28 mg) and dry (5.15 mg) weights of shoot were found in

control (no weed extract). On the other hand, minimum fresh (3.19 mg) and dry

(2.56 mg) weights were recorded in unboiled extract of Echinochola colonum

(Table 4.1).

In case of boiled extract, maximum fresh (8.71 mg) and dry (5.29 mg) weights of

shoot were recorded in control and minimum fresh (2.75 mg) and dry (1.50 mg)

weights of shoot were recorded in extract of Echinochola colonum (Table 4.2).

4.2 Allelopathic effect of different weed plant parts on rice

Khuda shama (Echinochola colonum) and sobuj nakful (Cyperus difformis) showed

more inhibitory effect as compared to other weed species, these two weed species

were selected for further investigation.

4.2.1 Effect of different weed plant parts on germination

Aromatic rice seed germination was affected significantly by allelopathic effect of

different weed plant parts (Tables 4.3-4.4). The highest germination (96.0%) was

observed in control (no weed extract) and the lowest germinations (70.5% and

78.8%) were recorded in stem extracts of khude shama (Echinochola colonum)

and sobuj nakful (Cyperus diformis), respectively. Days required to complete

germination were minimum (3.00 days) in control treatment and maximum (7.87

days) in whole plant extract of khude shama. Again days required to complete

germination were minimum (3.00 days) in control treatment and maximum (7.12

days) in stem extract of sobuj nakful (Cyperus difformis). When the effects of

different plant parts of weeds were compared, it was found that the highest reduction

was caused by stem extracts of different weeds and the lowest reduction was caused

by root extracts. The type and age of plant tissues are extremely important since

compounds are not uniformly distributed in the plants. Here, variation in allelopathic

effect of different weed plant parts might be due to type and age weed plant

(Gamez et al., 2002). Roy (1995) found that dried mass of stem of weeds like

Polygonum hydropiper, Amaranthus spinosus, Chenopodium album, Cyperus

rotundus and Imperata cylindrica were more detrimental than leaf and root. Kalita

et al. (1999) also found that shoot extracts of C. dactylon and C. rotundus was

more inhibitory than root extracts. Sharma et al. (2005) evaluated the allelopathic

effects of some newly developed strains of harar (Terminalia chebula) and reetha

(Sapindus mukorossi) on wheat (Triticum aestivum), maize (Zea mays), lentil

(Lens culinaris), pea (Pisum sativum) and brinjal (Solanum melongena). The

treated crops responded differently to aqueous leaf extracts of harar and reetha

indicating the presence of different phytoactive compounds which were either

phytotoxic or germination and growth promoters.

4.2.2 Effect of different weed plant parts on primary growth

4.2.2.1 Root and shoot lengths

Root and shoot lengths differed significantly due to the effect of extracts of different

plant parts of two weed species viz., khude shama (Echinochola colonum) and sobuj

nakful (Cyperus difformis). These two weed species were selected as per their

inhibitory effects on aromatic rice crops under investigation as reported in Tables

4.3-4.4 and Appendix is IIIa-IIIb, respectively.

Root and shoot lengths of aromatic rice seedling were affected significantly by the

allelopathic effect of different plant parts. Results revealed that the highest root

length (8.13 cm) of aromatic rice seedling was recorded in control treatment. The

lowest root length (2.73 cm) was recorded in root extract of khude shama (Echinochola

colonum) and minimum root length (1.25 cm) was found in stem extract of sobuj

nakful (Cyperus difformis). Again, the lowest shoot length (0.70 cm) was recorded

in root extract of khude shama and minimum shoot length (1.30 cm) was found in

stem extract of sobuj nakful (Tables 4.3-4.4). Agarwal et al. (2002) observed that

the weed extracts of C. rotundus and P. hydropiper inhibited the length of plumule in

all varieties of rice. Aqueous extracts of C. rotundus was found to reduce the

germination and seedling growth of okra (Ameena and George, 2002). Similar

inhibitory effect of the weed on vegetables was also noted by Binita et al. (2001).

4.2.2.2 Fresh and dry weights of root

Fresh and dry weights of root of aromatic rice seedling varied significantly due to

the effect of extract of different weed plant parts (Tables 4.3-4.4 and Appendix

IIIa-IIIb). Aromatic rice seeds with weed extract reduced fresh and dry weights of

root. Maximum fresh (7.00 mg) and dry (4.50 mg) weights of root was recorded

in control treatment and minimum fresh (3.19 mg and 1.08 mg) and dry (2.22 mg

and 0.90 mg) weights was due to stem extract of two weeds (Tables 4.3-4.4). Fresh

and dry weights of root of aromatic rice seedling were significantly affected due to

the allelopathic effect of weed plants parts.

4.2.2.3 Fresh and dry weights of shoot

Fresh and dry weights of shoot of aromatic rice seedling were significantly reduced

due to the allelopathic effect of weed plant parts as shown in Tables 4.3-4.4 and

Appendix is IIIa-IIIb. Maximum fresh (8.50 mg) and dry (5.72 mg) weights of

shoot were recorded in control while minimum fresh (1.53 mg and 2.95 mg) and

dry (0.48 mg and 2.11 mg) weights were observed due to the root and stem extracts

of two weeds, respectively. This finding might be due to the allelopathic potential

of these two weeds under consideration.

Table 4.1 Effect of unboiled weed extracts on germination and early growth of aromatic rice cv. BRRI dhan50 (Banglamoti)

Experimental treatments

Germination

(%)

Days to

complete

germination

Root

length

(cm)

Shoot

length

(cm)

Fresh

weight of

root (mg)

Dry weight

of root

(mg)

Fresh weight

of shoot

(mg)

Dry weight

of shoot

(mg)

Control 96.2 3.00 8.25 9.87 5.81 4.25 8.28 5.15

Joina (Eimbristylis miliacea) 91.6 4.75 4.13 4.00 2.90 2.10 5.33 4.35

Mutha (Cyperus rotundus) 89.3 4.33 4.85 5.35 3.85 2.18 4.91 3.10

Khude shama (Echinochola colonum) 80.8 7.00 3.50 4.00 2.17 1.53 3.19 2.56

Sobuj nakful (Cyperus difformis) 82.5 6.00 3.89 4.40 2.50 2.00 3.50 2.90

Foskabegun (Physalis heterophylla) 93.0 4.28 7.80 8.00 5.40 3.39 8.12 5.12

Chapra (Elusine indica) 91.0 5.10 6.80 7.48 4.80 3.00 7.12 4.95

LSD 0.8 0.15 0.24 0.23 0.27 0.15 0.22 0.16

Level of significance ** ** ** ** ** ** ** **

CV (%) 6.3 6.2 5.3 6.2 7.1 6.1 6.3 8.2

** Significant at 1% level of probability

Table 4.2 Effect of boiled weed extracts on germination and early growth of aromatic rice cv. BRRI dhan50 (Banglamoti)

Experimental treatments

Germination

(%)

Days to

complete

germination

Root

length

(cm)

Shoot

length

(cm)

Fresh

weight of

root (mg)

Dry weight

of root

(mg)

Fresh weight

of shoot

(mg)

Dry weight

of shoot

(mg)

Control 95.5 4.10 8.00 9.50 6.25 4.15 8.71 5.29

Joina (Eimbristylis miliacea) 91.2 4.00 4.10 3.80 2.80 2.00 5.10 4.00

Mutha (Cyperus rotundus) 90.3 4.25 4.00 4.10 2.50 1.98 4.05 3.33

Khuda shama (Echinochola colonum) 75.5 6.23 3.25 4.00 2.16 1.20 2.75 1.50

Sobuj nakful (Cyperus difformis) 83.3 5.80 3.60 4.25 2.79 1.56 2.89 1.73

Foskabegun (Physalis heterophylla) 92.8 4.00 7.40 7.80 5.33 3.20 8.00 5.00

Chapra (Elusine indica) 90.3 4.75 6.40 7.25 4.50 2.90 7.11 4.73

LSD 0.3 0.41 0.43 0.24 0.23 0.11 0.10 0.57

Level of significance ** ** ** ** ** ** ** **

CV (%) 7.7 17.7 7.4 9.9 2.4 4.7 4.3 4.1

** Significant at 1% level of probability

4.3 Allelopathic effect of extracts of different weed plant parts at different

concentrations

4.3.1 Interaction effect of weed plant parts and extract concentrations on

germination

The germination of aromatic rice was significantly influenced due to the interaction

effect of weed plant parts and different concentrations of extract (Tables 4.5-4.6

and Appendix is IVa-IVb). The highest germination (97.0%) was found in control

treatment while the lowest germination (64.0%) was found in 25% stem extract of

Echinochola colonum (Table 4.5). Again, the highest number of days (8.00 days)

required to complete germination was found in 25% stem extract of Echinochola

colonum (Table 4.5). The concentration of 25% was observed the most inhibitory

than those of 5% and 10% concentrations. This might be due to the fate of increasing

concentration of allelochemicals. Bora et al. (1999), Kalita et al. (1999a) and

Ameena and George (2002) noted more or less similar findings. Channappagoudar et

al. (2005) and Yao et al. (2006) found that increasing concentration of weed extracts

increased degree of inhibition for many plant species. The lowest number of days

(3.00 days) was found in control treatment. These findings indicated that the

presence of weed plant parts of Echinochola colonum had the retarding effect on

aromatic rice germination. This influence might be found due to its allelopathic

characteristics.

4.3.2 Interaction effect of weed plant parts and extract concentrations on

initial growth

Significant variation in root and shoot lengths of aromatic rice cv. BRRI dhan50

seed was observed due to the interaction effect of weed plant parts and extract

concentrations of weed plant parts (Tables 4.5-4.6). The highest root (8.10 cm)

and shoot (9.25 cm) length were found in control treatment. The lowest root (0.98

cm) and shoot (1.09 cm) lengths were obtained in 25% stem extract of Cyperus

difformis. The lowest root length was statistically similar with the effect of 25%

stem extract of Echinochola colonum and 10% stem extract, 10% and 25% root

extracts of Echinochola colonum (Tables 4.5-4.6).

A significant interaction between weed plant parts and extract concentration was

observed on fresh and dry weights of root of aromatic rice seedling. Maximum fresh

(6.13 mg) and dry (4.50 mg) weights of root were found in control treatment and

minimum fresh (0.55 mg) and dry (0.50 mg) weights of root were recorded in 25%

root extract of Echinochola colonum. Maximum fresh (6.13 mg) and dry (4.50 mg)

weights of root were found in control treatment and minimum fresh (1.04 mg) and

dry (0.58 mg) weights of root were recorded in 25% stem extract of Cyperus

difformis. Here, it was noted that fresh weight of root was statistically similar with

5% and 10% root extract; 5%, 10% and 25% leaf extract; 5%, 10% and 25% stem

extract and 10% and 25% whole plant. Again, dry weight was statistically similar

with 25% stem extract, 25% whole plant extract, 25% leaf extract and 10% root

extract of Echinochola colonum (Table 4.5).

Significant interaction between weed plant parts and extract concentrations was

observed on fresh and dry weights of shoot of aromatic rice seedling (Table 4.5).

Maximum fresh weight of shoot (8.60 mg) was found in control and minimum weight

of shoot (3.15 mg) was observed 25% stem extract of Echinochola colonum (Table

4.5). Maximum dry weight of shoot (5.40 mg) was found in control and minimum

dry weight of shoot (2.00 mg) was recorded in 25% stem extract of Echinochola

colonum. Again, maximum fresh weight of shoot (8.60 mg) was found in control and

minimum weight of shoot (2.25 mg) was observed 25% leaf extract of Cyperus

difformis (Table 4.5). Maximum dry weight of shoot (5.40 mg) was found in

control and minimum dry weight of shoot (0.89 mg) was recorded in 25% leaf

extract of Cyperus difformis (Table 4.6).

Table 4.3 Allelopathic effect of khude shama extract from different plant parts on germination and early growth of aromatic rice cv.

BRRI dhan50 (Banglamoti)

Treatments

Germination

(%)

Days to

complete

germination

Root

length

(cm)

Shoot

length

(cm)

Fresh weight

of root

(mg)

Dry weight

of root

(mg)

Fresh weight

of shoot

(mg)

Dry weight

of shoot

(mg)

Control 96.0 3.00 8.13 9.25 7.00 4.50 8.50 5.72

Leaf 78.0 7.00 2.83 1.15 3.45 2.90 1.75 0.70

Stem 70.5 7.00 2.98 0.97 3.19 2.22 1.61 0.68

Root 80.6 7.60 2.73 0.70 3.52 2.79 1.53 0.48

Whole plant 74.5 7.87 3.16 0.92 3.50 2.96 1.75 0.72

LSD 1.7 0.67 0.16 0.09 0.33 0.24 0.26 0.05

Level of

significance ** ** ** ** ** ** ** **

CV (%) 12.1 3.6 6.2 4.5 8.9 7.6 10.1 6.9

** Significant at 1% level of probability

Table 4.4 Allelopathic effect of sobuj nakful extract from different plant parts on germination and early growth of aromatic rice cv.

BRRI dhan50 (Banglamoti)

Treatments

Germination

(%)

Days to complete

germination

Root length

(cm)

Shoot length

(cm)

Fresh weight

of root (mg)

Dry weight

of root (mg)

Fresh weight

of shoot (mg)

Dry weight

of shoot (mg)

Control 96.0 3.00 8.13 9.25 7.00 4.50 8.50 5.72

Leaf 80.0 6.60 1.89 1.96 1.82 1.47 3.62 2.98

Stem 78.8 7.12 1.25 1.30 1.08 0.90 2.95 2.11

Root 83.8 6.73 1.73 2.20 1.73 1.19 3.20 2.90

Whole plant 81.3 6.41 2.10 1.95 1.96 1.52 2.98 2.11

LSD 1.7 0.24 0.14 0.21 0.11 0.23 0.09 0.18

Level of

significance ** ** ** ** ** ** ** **

CV (%) 8.3 8.2 5.2 9.8 9.2 7.5 7.4 4.1

** Significant at 1% level of probability

4.4 TLC Techniques for extraction of khude shama (Echinochola colonum)

and sobuj nakful (Cyperus difformis)

TLC plates of alcoholic extracts were developed by three pure solvents and three

mixed solvents. Pure solvents were ethanol (100%), methanol (100%) and mixed

solvents were ethanol: methanol (1:1), ethyl acetate: ethanol (1:1) and benzene :

ethyl acetate (1:1). Rf values of different spots appeared under iodine vapour have

been presented in Table 4.7. The developed TLC plates have been presented in

Fig. 4.5.

Table 4.5 Interaction effect of khude shama extract from different plant parts on germination and growth of aromatic rice cv. BRRI

dhan50 (Banglamoti)

Plant parts × Extract

concentration

Germination

(%)

Days to complete

germination

Root length

(cm)

Shoot length

(cm)

Fresh weight

of root (mg)

Dry weight

of root (mg)

Fresh weight

of shoot (mg)

Dry weight

of shoot (mg)

Control 97.0 3.00 8.10 9.25 6.13 4.50 8.60 5.40

Leaf

5% 80.0 7.79 2.50 2.70 1.15 0.80 3.80 2.95

10% 75.0 7.70 2.15 2.35 1.05 0.70 3.73 2.81

25% 70.0 7.30 2.00 2.30 0.83 0.50 3.58 2.49

Stem

5% 81.2 7.79 1.25 3.00 1.12 0.88 3.35 1.83

10% 68.5 7.75 1.23 2.78 0.97 0.77 3.25 2.15

25% 64.0 8.00 0.98 2.65 0.65 0.63 3.15 2.00

Root

5% 78.0 7.30 1.50 2.75 0.82 0.59 3.50 2.81

10% 72.0 7.45 1.40 2.70 0.65 0.55 3.43 2.70

25% 66.0 7.60 1.30 2.55 0.55 0.50 3.33 2.62

Whole plant

5% 82.0 6.80 1.45 3.15 1.75 0.90 3.60 2.79

10% 80.0 6.90 1.43 2.95 1.25 0.70 3.50 2.83

25% 75.0 7.30 1.35 2.78 0.98 0.50 3.43 2.75

LSD 0.98 0.07 0.06 0.29 1.38 0.06 0.13 0.16

Level of significance ** ** ** ** ** ** ** **

CV (%) 1.6 6.6 29.0 17.6 37.1 46.6 13.0 14.2

** Significant at 1% level of probability

Table 4.6 Interaction effect of sobuj nakful extract from different plant parts on germination and growth of aromatic rice cv.

BRRI dhan50 (Banglamoti)

Plant parts × Extract

concentration

Germination

(%)

Days to complete

germination

Root length

(cm)

Shoot length

(cm)

Fresh weight

of root (mg)

Dry weight

of root (mg)

Fresh weight

of shoot (mg)

Dry weight of

shoot(mg)

Control 97.0 3.00 8.10 9.25 6.13 4.50 8.60 5.40

Leaf

5% 81.2 6.45 1.90 2.11 2.15 1.55 2.95 2.25

10% 79.9 6.55 1.53 1.87 1.96 1.50 2.30 1.96

25% 77.0 6.60 1.45 1.80 1.70 1.20 2.25 0.89

Stem

5% 73.3 6.88 1.35 1.35 1.53 1.05 2.90 1.99

10% 73.2 6.96 1.12 1.27 1.32 0.88 2.84 1.71

25% 70.2 7.11 0.98 1.09 1.06 0.70 2.51 1.39

Root

5% 80.1 6.53 2.11 2.11 2.12 0.93 2.99 1.70

10% 78.1 6.68 1.19 1.71 1.90 0.79 2.83 1.73

25% 73.9 6.73 0.97 1.15 1.04 0.58 2.42 1.52

Whole plant

5% 83.0 6.23 1.60 2.15 1.97 1.15 3.12 1.80

10% 81.2 6.32 1.79 1.90 1.70 0.85 2.80 1.10

25% 79.7 6.40 1.60 1.68 1.55 0.65 2.40 1.10

LSD 0.98 0.29 0.17 0.09 0.14 0.08 0.04 0.16

Level of significance ** ** ** ** ** ** ** **

CV (%) 1.4 6.5 29.1 26.8 23.4 33.5 17.4 23.6

** Significant at 1% level of probability

Table 4.7 TLC of weed extracts and Rf values of the spot

Weeds Extracting

solvent

Carrier solvent Rf values

C1 C2 C3

Khude shama

(Echinochlola colonum)

Ethanol

Ethanol (100%) 0.83 0.78 0.087

Methanol (100%) 0.86 0.85 0.043

Ethyl acetate (100%) 0.87 0.72 0.80

Ethanol : Methanol (1:1) 0.77 0.75 0.025

Ethyl acetate :

Ethanol (1:1) 0.83 0.80 0.82

Benzene : Ethyl

acetate (1:1) 0.53 0.55 0.54

Sobuj nakful

(Cyperus difformis)

Ethanol (100%) 0.75 0.74 0.104

Methanol (100%) 0.89 0.88 0.034

Ethyl acetate (100%) 0.83 0.80 0.81

Ethanol : Methanol (1:1) 0.76 0.76 0.021

Ethyl acetate :

Ethanol (1:1) 0.83 0.81 0.80

Benzene : Ethyl

acetate (1:1) 0.54 0.55 0.50

A B

Fig. 4.5 TLC plates of weed extract of khude shama (Echinochola colonum) and

sobuj nakful (Cyperus difformis) in ethanol eluted by mixed solvents (A)

ethyl acetate: ethanol (1:1) and (B) benzene : ethyl acetate (1:1)

Thin layer chromatographic (TLC) studies of the extracts indicated that compounds

present had high to low polarity. Their Rf values have been reported in Table 4.7.

The concentrations of these compounds in weed extracts were low. So, for obtaining

higher concentration of the compounds in the extracts had also for better bioactivity,

vigorous extract conditions seemed to be needed. The bioactivities of extracts were due

to the high polar organic compounds present in these weed extracts. Another observation

of TLC technique, of these extracts indicated that organic solvents and vigorous extract

conditions were better for extraction of these weeds. In TLC techniques, three unknown

compounds were identified from both extracts of khude shama (Echinochola colonum)

and sobuj nakful (Cyperus difformis). Probably, one or mixture of compounds of

high polarity from the detected compounds might be responsible for the allelopathic

effect on germination and growth of the test crop. Further investigation is needed to

identify the specific or actual compounds responsible for allelopathic action.

CHAPTER 5

SUMMARY AND CONCLUSION

A laboratory experiment was conducted at the Department of Agricultural Chemistry,

Bangladesh Agricultural University, Mymensingh to evaluate the allelopathic potential

of six selected weed species viz., joina (Eimbristylis miliacea), mutha (Cyperus

rotundus), khude shama (Echinochola colonum), sobuj nakful (Cyperus difformis),

foskabegun (Physalis heterophylla) and chapra (Elusine indica) on seed germination

and primary growth of aromatic rice cv. BRRI dhan50 (Banglamoti). The effect of

different weed plant parts e.g. root, stem, leaf and whole plant and three concentrations

viz., 5, 10 and 25% (w/v) of the extracts were evaluated.

Weed species were collected from the Agronomy Field Laboratory, Bangladesh

Agricultural University, Mymensingh. Weed species were washed, chopped and

macerated. In a set, 250 g fresh weed mass of each weed species was boiled in 1 L

water and kept for 3 days with intermittent stirring. After filtration, the filtrates

were used as boiled extracts of weeds. In another set, 250 g fresh weed mass were

decomposed in 1 L water for 7 days at room temperature. The extracts were filtered

and used as unboiled extract. In another trail, the collected plants were separated

into four parts such as leaves, stems, roots and whole plants. Fresh weed plants

parts were chopped and decomposed in 500 mL distilled water for 7 days at room

temperature (28 1°C) with intermittent stirring. After filtration 5, 10 and 25%

(w/v) extract solutions were prepared from each part of two selected weeds.

Germination of aromatic rice seeds was studied by petridish method. Measurement of

shoot and root lengths were started on 14 days after seed placement. After 2 days,

seedlings were collected and fresh and dry weights were recorded.

The aqueous extracts of different weed species exhibited significant inhibitory

influence on aromatic rice. The ranking of weed species in respect of inhibitory

effect on seed germination aromatic rice was Echinochola colonum > Cyperus difformis

> Cyperus rotundus > Elusine indica > Eimbristylis miliacea > Physalis heterophylla.

Khude shama (Echinochola colonum) and sobuj nakful (Cyperus difformis) had strong

detrimental effect on the primary growth of aromatic rice. The effect of unboiled

and boiled extracts of these weed species showed significant reduction in germination

and initial growth of aromatic rice.

The aqueous extract of different parts (root, stem, leaf and whole plant) of the selected

weed species reduced seed germination, root length, shoot length and dry matter

production and increased days to complete seed germination of aromatic

rice. The highest reduction in aromatic rice seed germination was caused by

Echinochola colonum and the lowest reduction was caused by Physalis heterophylla.

In case of root and shoot lengths, the harmful effect of Echinochola colonum was

greater than all other selected weeds. The highest reduction was noticed from the

high concentration (25%) of the extract. The dry matter production was also affected

by extracts of the selected weeds due to their differential allelopathic effects.

Thin layer chromatographic (TLC) technique was developed to identify the

chemical using different polar and non polar solvent systems such as ethanol,

methanol, ethyl acetate and benzene. In TLC technique, three unknown compounds

were identified in the extracts of khude shama (Echinochola colonum) and sobuj

nakful (Cyperus difformis). Probably, one or mixture of the detected compounds

might have special constituents which would be responsible for the allelopathic effect

on germination and early growth of the test crop.

It is, therefore, concluded that all selected weeds had more or less inhibitory effect on

seed germination, number of days to complete germination, root and shoot lengths,

fresh and dry weights of root and shoot of aromatic rice BRRI dhan50. Among the

plant parts, stem extract was the most inhibitory. From the above findings of present

experiment, it could be suggested than khude shama (Echinochola colonum) and

sobuj nakful (Cyperus difformis) had strong detrimental effect on aromatic rice. Therefore,

the cited weeds must be taken into well care and it should be avoided from the aromatic

rice field during land preparation. The experimental results proved that it was

important to exclude these allelopathic weeds especially khude shama (Echinochola

colonum) and sobuj nakful (Cyperus difformis).

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APPENDICES

Appendix I. Analysis of the variance of the data of unboiled weed extract on

seed germination and early growth of aromatic rice cv. BRRI

dhan50

Source of

variation

Degrees

of

freedom

Mean square

Germination

(%)

Root

length

(cm)

Shoot

length

(cm)

Fresh wt.

of root

(mg)

Dry wt.

of root

(mg)

Fresh wt.

of shoot

(mg)

Dry wt.

of

shoot

(mg)

Day of

complete

germination

Treatment 6 114.184** 24.737** 29.004** 12.895** 5.275** 13.992** 3.723** 7.05**

Error 12 12 1 0.014 0.008 0.008 0.009 0.007 0.0419

**Significant at 1% level of probability

Appendix II. Analysis of the variance of the data of boiled weed extract on seed

germination and early growth of aromatic rice cv. BRRI dhan50

Source of

variation

Degrees

of

freedom

Mean square

Germination

(%)

Root

length

(cm)

Shoot

length

(cm)

Fresh wt.

of root

(mg)

Dry wt.

of root

(mg)

Fresh wt.

of shoot

(mg)

Dry wt.

of

shoot

(mg)

Day of

complete

germination

Treatment 6 160.08** 22.822* 28.399* 12.648** 4.847** 14.298** 3.767** 4.976**

Error 12 1 0.008 0.018 0.01 0.009 0.01 0.015 0.028

**Significant at 1% level of probability and *Significant at 5% level of probability

Appendix IIIa. Analysis of the variance of khude shama extract obtained from

different plant parts of extract concentration on seed

germination and growth of aromatic rice cv. BRRI dhan50

Source of

variation

Degrees

of

freedom

Mean square

Germination

(%)

Root

length

(cm)

Shoot

length

(cm)

Fresh wt.

of root

(mg)

Dry wt.

of root

(mg)

Fresh

wt. of

shoot

(mg)

Dry wt.

of

shoot

(mg)

Day of

complete

germination

Treatment 3 57.39** 0.074** 0.1** 0.046** 0.455** 0.051** 0.042** 0.351**

Error 8 0.75 0.003 0.001 0.005 0.001 0.001 0.004 0.006

**Significant at 1% level of probability

Appendix IIIb. Analysis of the variance of sobuj nakful extract obtained from

different plant parts of extract concentration on seed

germination and growth of aromatic rice cv. BRRI dhan50

Source of

variation

Degrees

of

freedom

Mean square

Germination

(%)

Root

length

(cm)

Shoot

length

(cm)

Fresh

wt. of

root

(mg)

Dry

wt.

of

root

(mg)

Fresh

wt. of

shoot

(mg)

Dry

wt.

of

shoot

(mg)

Day of

complete

germination

Treatment 3 18.37** 0.432** 0.38** 0.39** 0.3** 0.212** 0.677 0.218NS

Error 8 0.76 0.008 0.008 0.003 0.008 0.005 0.008 0.758

**Significant at 1% level of probability and NS = Not significant

Appendix IVa. Analysis of the variance of khude shama extract obtained from

different plant parts and extract concentration on seed

germination and growth of aromatic rice cv. BRRI dhan50

Source of

variation

Degrees

of

freedom

Mean square

Germination

(%)

Root

length

(cm)

Shoot

length

(cm)

Fresh

wt. of

root

(mg)

Dry wt.

of root

(mg)

Fresh

wt. of

shoot

(mg)

Dry wt.

of

shoot

(mg)

Day of

complete

germination

Treatment 12 232.74** 10.166** 9.432** 7.473** 2.905** 6.016** 2.064** 2.821**

Error 26 1 0.003 0.083 1.986 0.003 0.016 0.025 0.004

**Significant at 1% level of probability

Appendix IVb. Analysis of the variance of sobuj nakful extract obtained from

different plant parts and extract concentration on seed

germination and growth of aromatic rice cv. BRRI dhan50

Source of

variation

Degrees

of

freedom

Mean square

Germination

(%)

Root

length

(cm)

Shoot

length

(cm)

Fresh

wt. of

root

(mg)

Dry wt.

of root

(mg)

Fresh

wt. of

shoot

(mg)

Dry wt.

of

shoot

(mg)

Day of

complete

germination

Treatment 12 137.464** 10.084** 12.906** 4.746** 2.582** 7.936** 3.567** 1.693**

Error 26 0.995 0.028 0.006 0.021 0.005 0.001 0.025 0.085

**Significant at 1% level of probability